24 pin supplies work with 20 pin motherboards.
There are two choices in the matter. If a power supply has a
"solid 24 pin", then when you go to plug it into the 20 pin
connector, you have to check for adjacent tall objects. Sometimes,
the left over pins will bump against a motherboard capacitor.
Most 24 pin power supplies, use a split 20+4 connector. There
is a tiny "hinge" between the 20 pin section and 4 pin section.
The four pin section has wires of four different colors. When you
need to use such a 20+4 supply with a 20 pin motherboard (something
I'm doing right now on my latest build), you move the 4 pin
section out of the way. It just dangles there in space, unused.
You have to be careful, not to mix up that 2x2 section with the
four different color wires, with the 2x2 connector that powers
the processor. The power supply will have a cable with two
yellow wires and two black wires, and that goes to the ATX12V
2x2 or 2x4 motherboard connector. On desktop motherboards
that provide room for a 2x4, they will usually place a sticker
over the four extra pins, to help guide you where to stick the
ATX12V 2x2 power supply connector. If your supply has a 2x4 with
four yellow and four black, you can plug that into the 2x4 if you
want. In a lot of situations, the usage of 2x4 is optional.
If would only be, if you were overclocking a Pentium D 805 processor
to 4 GHz, where the processor ends up drawing 200W, where the
2x4 connector is essential. For many other cases, the power consumption
is low enough, that a 2x4 is "window dressing" rather than a
necessity.
Some pictures of doing this stuff, are here.
http://www.playtool.com/pages/psuconnectors/connectors.html
The 20+4 type, shown unhinged and ready for a 20 pin motherboard.
The missing pin on the 20 pin section, is the obsolete -5V pin.
http://www.playtool.com/pages/psuconnectors/main20plus4index.jpg
This is what plugging a "solid 24" into a 20 pin motherboard looks like.
The four pins on the end hang over. They're redundant, and give the
connector scheme more current carrying capacity. There are only
certain situations where such a capacity is required (running
SLI with a couple 6600GT for example, where the 12V mobo current
approaches 8 amps). If you own a single video card, even a GTX 580,
the 20 pin connector remains sufficient for the current flow.
If there was a tall electrolytic right near the end of the
connector, it could bump into the four extra pins. Yes,
it has happened. Some people have no luck.
http://www.playtool.com/pages/psuconnectors/24in20.jpg
And for completeness, this is plugging a 20 pin, into a 24 pin
motherboard. The way the connectors work, is pin 1 should
always line up with pin 1, and the interconnection scheme is
guided by the shapes of the individual pins. That helps
prevent an illegal alignment. If the connector won't slide
into place, inspect the shapes to be sure you're doing it
right. The lock latch on both connector pieces, should
at least guide you to the right 180 degree rotation. The
lock latches should be on the same side.
http://www.playtool.com/pages/psuconnectors/20in24.jpg
*******
This is the connector on the FSP550-60PLG. It is a solid 24 pin
type, with *no* hinge visible. The manufacturer could change
this at any time, so it's hard to say whether the picture
is accurate in all cases.
http://images10.newegg.com/NeweggImage/productimage/17-103-478-06.jpg
Now, go inspect your 20 pin motherboard, for
capacitors that could "bump" into the redundant
4 pin section that will be "hanging over".
HTH,
Paul
